1. Field of the Invention
The present invention relates to a power management device and computer readable medium storing a program for effectively preventing the battery of a vehicle from running out while the vehicle is parked.
2. Description of the Related Art
Conventionally, to drive the electric components mounted on a vehicle, a battery for supplying power to the electric components and an alternator (a power generator) for charging the battery are also mounted on the vehicle. The power generating capacity of the alternator is determined in accordance with the state of the battery and the driving states of the electric components, and an engine. ECU (electronic control unit) notifies the alternator of the power generating capacity.
In recent years, the number of electric components mounted on each vehicle has been increasing, and this trend is expected to continue. Therefore, there is a demand for higher charge control precision or sophisticated charge control for preventing battery degradation.
One of the problems caused with the increase in the number of electric components is dark current. Dark current is the current to be consumed by the electric components while the engine is stopped. For example, an antitheft security device for cars has a large amount of dark current, mainly because such a device is in operation even when the engine is stopped. If the amount of dark current increases, the battery might deteriorate and run out.
To prevent such running out of a battery, Japanese Unexamined Patent Publication No. 2004-147460 discloses a technique by which the target value of the charge amount (SOC: state of charge) of the battery is determined in accordance with a destination that is set through a navigation device, and the battery is charged to achieve the target value of the charge amount (SOC) before the vehicle arrives at the destination.
However, the technique disclosed in Japanese Unexamined Patent Publication No. 2004-147460 has the problem of being unable to effectively prevent running out of the battery, because the target value of the charge amount might not be reached when there is a change in the traffic condition or the climate or when there is a change in the usage state of the electric components. Also, the target value of the charge amount is determined by predicting whether the vehicle is to be parked for a short period of time or a long period of time, based on the destination. However, there is no guarantee that the prediction is accurate, and the therefore, the problem of being unable to effectively prevent a battery from running out remains.